Foot molding



July 14, 1959 M', H BmNms 2,894,288

FOOT MOLDING Filed June 26, 1957 United States Patent O FOOT MOLDING Marvin H. Brindis, Haverhill, Mass. Application June 26, 1957, Serial No. 668,242

`3 Claims. (Cl. 1li-55.05)

`This invention relates to a method of making accurate molds-l of human feet from which casts duplicating the feet can be made.

Heretofore in making custom shoes it has been the common practice to make a mold impression of the feet from plaster of Paris or the like. Processes based on the use of this material have a number of undesirable aspects. The material :is hard to work with and requires a lengthy setting time which is uncomfortable for the patient. Furthermore the mold must be made in several parts to permit the withdrawal of the foot. This usually requires a sharp instrument to separate the cast `sections which is both uncomfortable and dangerous to the patient. Plaster in hardening evolves discomforting heat which may cause the foot to swell creating pressure. Also hair on the foot must be shaved or well lubricated to prevent it frombecoming embedded in the plaster. For these and other reasons methods utilizing plaster are awkward, `time consuming and unpleasant to the patient. Furthermore the necessity of making molds in several sections reduces the resulting accuracy.

Objects of `the present invention are to provide a method of making casts of a human foot in one piece, which is quicker, less painful, less dangerous and more accurate, Further objects ,are to provide a method which is easier for the operator and which provides accurate molds of thev feet without .the evolution" of heat. Still further objects are to provide a method of making a foot mold where the foot is either at ,rest or under weightb'earingstress, as desired, and which permits the operator to see and properly position the foot as a bottom impression is being made.

According to this invention the method of forming an accurate foot mold comprises embedding the bottom of a foot in a layer of settable material, allowing the material to set, covering the foot with a liquid material which sets to form an elastic form-retaining mold, and after the liquid material has set, withdrawing the foot from the mold by elastically spreading the mold opening. As desired, the foot can be at rest or the foot can be pressed against the set bottom material to cause it to elongate before covering the upper part of the foot. Preferably the impression of the lower portion of a foot and of the upper portion of a foot are made from the same material compounded to different elastic consistencies, the upper material being more elastic than the bottom material. While other materials may be used, the impression material preferably comprises soluble salts of alginic acid compounded with a substantially greater quantity of water in the case of the upper impression material than for the lower impression material.

One embodiment of this invention is illustrated in the accompanying drawing in which Fig. 1 is a side elevation in section of a container having a layer of liquid impression material therein;

Fig. 2 is a similar View showing a foot embedded in the material;

ice

Fig. 3 is a similar view after the upper material has been poured;

Fig. 4 is a similar view after the material has set and the foot withdrawn, showing the cavity being filled with casting material; and

Fig. 5 is a side elevation of a cast made from the foot mold.

Referring to the drawings, a rectangular container 1 or the `like is utilized. A layer of settable material 2 is placed in the bottom of the pan 1 to a suitable depth, for example to a depth of from one to two inches. The patient is seated in a chair and the spacing between the bottom of his foot and the bottom of the container is adjusted. This adjustment is best accomplished by hav ing the patient sit in a vertically adjustable chair. It can also be accomplished by using spacer bars beneath the veall and the heel of the foot to properly determine the distance from the sole of the foot and the bottom of the container. No weight should be placed on such spacer bars.

The patients foot is embedded in the settable material 2 which should cover the bottom of the floot to approximately just below the nail line of the toes. The heel of `the foot should preferably be slightly higher than the ball of the foot. While it is preferred to place the layer ,of settable material 2 in the bottom of the container 1 and then to insert and embed the bottom of the foot therein as illustrated, the foot can lirst be inserted into the empty container particularly where spacer bars are used therein, and the liquid settable material 2 thereafter poured into the container to the proper depth.

After the lower impression material 2 has set to a consistency suflicient to support the foot without substantial deformation, the foot is covered with a liquid impression material 3 which sets to form an elastic form- `retaining mold. This material is then allowed t0 set. The f oot is thereafter withdrawn from the mold by elastically spreading the mold opening for example by ilexing the muscles of the foot as it is withdrawn.

It should be noted that throughout the above procedure the patient has been seated and that full weight has not been placed on the foot. By this means the outline of the foot at rest is captured by the two layers of impression material. It is often desirable however to capture the outline of the foot under weightbearing stress to determine its shape and size in walking and standing. For this purpose the patient stands on the lower impression material 2 after it has set to cause the foot to spread and elongate. The liquid upper impression material 3 is then poured to cover the foot and allowed to set while the foot is thus under stress. This method of capturing the bottom contour of the foot at rest while the balance of the mold reproduces the elongated foot permits a more comfortable shoe to be made.

After the mold has set and the foot has been withdrawn, a cast duplicating the foot is made as illustrated in Fig. 4. A casting material 5, usually plaster of Paris, is poured into the mold opening from a ladle 6. The toe of the mold should be somewhat lower than the heel and the mold vibrated during pouring to assure that the casting material 5 completely iills the mold cavity without entrapping air. The cast is preferably made as soon after the mold has set as possible to avoid any subsquent dimensional change of the mold impression materials 2 and 3. After the casting material 5 has set, the cast 7 is withdrawn from the mold by again flexing the elastic impression materials 2 and 3 or by destroying the mold if no further casts are needed. The finished cast is illustrated in Fig. 5.

The impression materials used should set to form elastic form-retaining molds which are sufficiently elastic v 2,894,288 Y Y i to allow withdrawal of the foot and yet which have suicient strength to retain their configuration during the pouring of a casting. Preferably these materials should permit compounding in various consistencies to give control over the elasticity of the two"moldportions.` i EX- amples of such materials useful in this invention are suitably compounded alginates,l agar-agar, gelatin, synthetic and natural' resin foamsgxsynthetic and. natural latexes, and Permaex CMC, a polymercaptan-base synthetie yresin' made .by .the Perma-Flex :Mold Co., Columbus, Ohio. Particularly suitable are alginate formulations set forthj in United vStates Patent 2,390,137, granted 'December 4, 1945. As set forth :in the abovementioned patent these formulationsjcomprise (l) soluble salts of al ginic acids, (2) a gelling agent, (3) a retarding agent and (4) substantiallyin'ert,fillers added to extend and give structural strength to the resultinggell. These alginate materials can Vbe compounded withvarious amounts of water to control the setting time and stillness or elasticity of the resulting gell. In the embodiment illustrated, the lower impressionlayer 2 preferably comprises about iive `parts, ofl alginate mixed with about thirty-two parts kby weight of water. Alginates so compounded have been ound to set to a stiff consistency suliicient to supportthe Weight of theleg and foot in ,about tive minutes. About Ififteen minutes is required yto support theV standing weight of the patient. If the above compoundingY water is reduced to twenty-four .prartsthel setting A time to support a standing patient is reduced to abouteight minutes'. rThe upper impression material 3`, preferably comprises about eleven parts of alginate andabout 96v'pa`rts of water. Alginates in this consistency have been found to set in about 15 minutes to a flexible gell which will permit the foot to be Withdrawn therefrom without'disrupting the gell and which yet proyide sufficient 'stiiiness to permit an accurate cast to be r'nade therefrom.l

Itshould be noted that applicants molds are poured in ytwo stagesl or steps, the'hirst` portion being less elastic than, the `seccn'd portion and' being lpermitted vto set before t'nefs'econd portion is poured. f This two step method has' lthe advantage of requiring only a short time for the patient to wait beforeihe can stand onthe initial gell without pushing through to the bottom of the container, 1

of permitting the patient to stand and thus cause the foot to spread and elongate before the upper portion of the mold is completed, and permitting the operator to see thefoot as the bottom mold ismadetoassure itsproperr positioning. It has been found that the two separate pourings of impression materials will, when set, adhere to each other and to the container with suticient force to permit the foot to be withdrawn therefrom and for the mold to be handled without causing the two portions to separate.

It should be understood that the present disclosure is for the purpose of illustration only and that the invention includes all equivalents and modifications within the scope of the appended claims.

I claim:

l. The method of forming an accurate `foot mold which comprises pouring into the mold a layer of settable material, allowing the material to set, pressing the foot against the set material partially to embed the foot in the material, while thus embedded covering the foot with liquid material which sets to form an elastic form-retaining mold which adheres to said bottom layer, and, after the liquid material has set, withdrawing the foot from the mold by elastically spreading the mold opening.

2. The method of forming an accurate foot mold which comprises embedding the bottom of a foot in a layer of liquid material in one consistency which sets to form a stiff form-retaining mold, allowing the material to set, pressing the foot against said layer, covering the foot with another layer of said material in a second which adheres to said bottom'layer, more elastic consistency, allowing the second layer to set, and withdrawing the yfoot from the mold by elastically spreading the mold opening.

3. The method of forming an accurate foot mold which comprises placing in the bottom of a container a layerof alginate impression material mixed in water to a consistency comprising about thirty-two parts water to fiveparts by weight alginate powder material, embedding the bottom of a foot in the material, allowing the material `to set, pressing the foot against said layer, covering the foot with a second layer of alginate impression rnaterial in a consistency ofabout ninety-six parts water to eleven parts alginate which adheres to said bottom layer, allowing the second layer to set,` and .withdrawing 4the foot from the mold .by elasticallyspreading the'mold `opening.y

References Citedin the le of this patent UNITED STATES PATENTS Sugarman etal. lApr. 3, v1951 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No., 2,894,288 July 14, 1959 Marvin H. Brindis It is herebY certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4v lines 25 and 26, strike out "which .adheres to said bottom layer," and insert the same after 'consistency," in line 261 same column 4.

signed and sealed this 16th day of August 1960.,

( SEAL) Attest:

KARL Hi AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents 

